The present invention relates to a method for making a plurality of solid tantalum capacitors on a valve-metal substrate, and more particularly to a low cost batch manufacturing method for making discrete flip-chip style capacitors.
There is disclosed in the U.S. Pat. to Millard et al, No. 3,889,357 issued June 17, 1975, assigned to the same assignee as is the present invention, a method for making capacitors by screen printing an array of pads of a tantalum containing ink on a tantalum substrate to form porous tantalum pads that will serve as capacitor anodes. After forming a tantalum oxide film over the pad surfaces, a solid electrolyte is formed by pyrolysis of manganous nitrate over the dielectric film. Special precautions and a series of special steps are taken to keep the MnO.sub.2 out of the streets that separate the pads of the array. A flip-chip style capacitor is also produced by welding separate nickel bars to the substrate adjacent to each pad, which process tends to be difficult to control.
An improved counterelectrode system for solid electrolyte capacitors is described by Cheseldine in U.S. Pat. application Ser. No. 830,310 filed Sep. 2, 1977, and assigned to the same assignee. It is also mentioned therein that the streets may be flooded with an insulating resin, and after curing the resin, slots are cut therein in which a conductive resin is cast to form anode terminals. This is also a difficult procedure to control since the height of the insulative resin layer is determinative of the height of anode terminals. An alternative anode terminal consists of a metal bar being welded to the substrate.
It is an object of the present invention to provide a low cost batch method for making a plurality of flip-chip-mountable solid electrolyte capacitors.
It is a further object of the present invention to provide such a method that is comprised of relatively easily executed and non-critical steps.